DNA topoisomerase IIα controls replication origin cluster licensing and firing time in Xenopus egg extracts.

ABSTRACT: Sperm chromatin incubated in Xenopus egg extracts undergoes origin licensing and nuclear assembly before DNA replication. We found that depletion of DNA topoisomerase IIα (topo IIα), the sole topo II isozyme of eggs and its inhibition by ICRF-193, which clamps topo IIα around DNA have opposite effects on these processes. ICRF-193 slowed down replication origin cluster activation and fork progression in a checkpoint-independent manner, without altering replicon size. In contrast, topo IIα depletion accelerated origin cluster activation, and topo IIα add-back negated overinitiation. Therefore, topo IIα is not required for DNA replication, but topo IIα clamps slow replication, probably by forming roadblocks. ICRF-193 had no effect on DNA synthesis when added after nuclear assembly, confirming

SUBMITTER: Gaggioli V 

PROVIDER: S-EPMC3753627 | biostudies-literature | 2013 Aug

REPOSITORIES: biostudies-literature